Page:Popular Science Monthly Volume 70.djvu/408

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POPULAR SCIENCE MONTHLY

NOTES ON THE DEVELOPMENT OF TELEPHONE SERVICE

By FRED DE LAND

Pittsburg, Pa.

IN November, 1876, Graham Bell perceived the value and efficiency of the metallic circuit and advised its adoption for telephone service to overcome the inductive annoyances. On February 1, 1878, the parent Bell company recommended the use of metallic circuits for

Fig. 30.

exchange service, although only three telephone companies had exchanges in operation that month. But many of the local companies could only perceive that the introduction of a metallic-circuit system meant double the cross-arm space, stronger poles, double the terminal

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